Superabrasive elements including coatings and methods for removing interstitial materials from superabrasive elements

ABSTRACT

A method of processing a polycrystalline diamond element is disclosed. The method may include depositing a vaporized material over a selected portion of a polycrystalline diamond element to form a protective coating over the selected portion. The polycrystalline diamond element may include a polycrystalline diamond table. The method may also include exposing at least a portion of the polycrystalline diamond element to a leaching solution such that the leaching solution contacts an exposed surface region of the polycrystalline diamond table and at least a portion of the protective coating. The method may also include removing the polycrystalline diamond element from the leaching solution. The protective coating may be substantially impermeable to the leaching solution.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/767,717, titled “SUPERABRASIVE ELEMENTS INCLUDING CERAMIC COATINGSAND METHODS OF LEACHING CATALYSTS FROM SUPERABRASIVE ELEMENTS” and filed26 Apr. 2010, which claims priority to U.S. Provisional PatentApplication No. 61/172,976, titled “SUPERABRASIVE ELEMENTS INCLUDINGCOATINGS AND METHODS FOR REMOVING INTERSTITIAL MATERIALS FROMSUPERABRASIVE ELEMENTS” and filed 27 Apr. 2009, the disclosures of whichare hereby incorporated, in their entirety, by these references.

BACKGROUND

Wear-resistant, superabrasive materials are traditionally utilized for avariety of mechanical applications. For example, polycrystalline diamond(“PCD”) materials are often used in drilling tools (e.g., cuttingelements, gage trimmers, etc.), machining equipment, bearingapparatuses, wire-drawing machinery, and in other mechanical systems.Other types of superabrasive materials, such as ceramics (e.g., cubicboron nitride, silicon carbide, and the like), are also utilized forsimilar applications.

Conventional superabrasive materials have found utility as superabrasivecutting elements in rotary drill bits, such as roller cone drill bitsand fixed-cutter drill bits. A conventional cutting element typicallyincludes a superabrasive layer or table, such as a PCD table. The PCDtable is formed and bonded to a substrate using an ultra-high pressure,ultra-high temperature (“HPHT”) process. The cutting element may bebrazed, press-fit, or otherwise secured into a preformed pocket, socket,or other receptacle formed in the rotary drill bit. In anotherconfiguration, the substrate may be brazed or otherwise joined to anattachment member such as a stud or a cylindrical backing. Generally, arotary drill bit may include one or more PCD cutting elements affixed toa bit body of the rotary drill bit.

Conventional superabrasive materials have also found utility as bearingelements in thrust bearing and radial bearing apparatuses. Aconventional bearing element typically includes a superabrasive layer ortable, such as a PCD table, bonded to a substrate. One or more bearingelements may be mounted to a bearing rotor or stator by press-fitting,brazing, or through other suitable methods of attachment. Typically,bearing elements mounted to a bearing rotor have superabrasive facesconfigured to contact corresponding superabrasive faces of bearingelements mounted to an adjacent bearing stator.

Superabrasive elements having a PCD table are typically fabricated byplacing a cemented carbide substrate, such as a cobalt-cemented tungstencarbide substrate, into a container or cartridge with a volume ofdiamond particles positioned on a surface of the cemented carbidesubstrate. A number of such cartridges may be loaded into a HPHT press.The substrates and diamond particle volumes may then be processed underHPHT conditions in the presence of a catalyst material that causes thediamond particles to bond to one another to form a diamond table havinga matrix of bonded diamond crystals. The catalyst material is often ametal-solvent catalyst, such as cobalt, nickel, and/or iron, thatfacilitates intergrowth and bonding of the diamond crystals.

In one conventional approach, a constituent of the cemented-carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. In this example, the cobalt acts as acatalyst to facilitate the formation of bonded diamond crystals. Often,a metal-solvent catalyst may be mixed with diamond particles prior tosubjecting the diamond particles and substrate to the HPHT process.

The metal-solvent catalyst may dissolve carbon from the diamondparticles and portions of the diamond particles that graphitize due tothe high temperatures used in the HPHT process. The solubility of thestable diamond phase in the metal-solvent catalyst may be lower thanthat of the metastable graphite phase under HPHT conditions. As a resultof the solubility difference, the graphite tends to dissolve into themetal-solvent catalyst and the diamond tends to deposit onto existingdiamond particles to form diamond-to-diamond bonds. Accordingly, diamondgrains may become mutually bonded to form a matrix of polycrystallinediamond, with interstitial regions defined between the bonded diamondgrains being occupied by the metal-solvent catalyst.

In addition to dissolving carbon and graphite, the metal-solventcatalyst may also carry tungsten and/or tungsten carbide from thesubstrate into the PCD layer. Following HPHT sintering, the tungstenand/or tungsten carbide may remain in interstitial regions definedbetween the bonded diamond grains.

The presence of the solvent catalyst in the diamond table is believed toreduce the thermal stability of the diamond table at elevatedtemperatures. For example, the difference in thermal expansioncoefficient between the diamond grains and the solvent catalyst isbelieved to lead to chipping or cracking in the PCD table of a cuttingelement during drilling or cutting operations. The chipping or crackingin the PCD table may degrade the mechanical properties of the cuttingelement or lead to failure of the cutting element. Further, at hightemperatures, diamond grains may undergo a chemical breakdown orback-conversion with the metal-solvent catalyst. Further, portions ofdiamond grains may transform to carbon monoxide, carbon dioxide,graphite, or combinations thereof, thereby degrading the mechanicalproperties of the PCD material.

Accordingly, it is desirable to remove a metal-solvent catalyst from aPCD material in situations where the PCD material may be exposed to hightemperatures. Chemical leaching is often used to remove metal-solventcatalysts, such as cobalt, from regions of a PCD article that mayexperience high temperatures, such as regions adjacent to the workingsurfaces of the PCD article. Conventional chemical leaching techniquesoften involve the use of highly concentrated and corrosive solutions,such as highly acidic solutions, to dissolve and remove metal-solventcatalysts from polycrystalline diamond materials.

However, in addition to dissolving metal-solvent catalysts from a PCDmaterial, leaching solutions may also dissolve portions of a substrateto which the PCD material is attached. For example, highly acidicleaching solutions may dissolve portions of a cobalt-cemented tungstencarbide substrate, causing undesired pitting and/or other corrosion ofthe substrate surface.

SUMMARY

The instant disclosure is directed to methods of processingpolycrystalline diamond elements. According to various embodiments, sucha method may comprise depositing a vaporized material over a selectedportion of a polycrystalline diamond element to form a protectivecoating (e.g., a ceramic coating) over the selected portion. Thepolycrystalline diamond element may comprise a polycrystalline diamondtable. The method may also comprise: 1) exposing at least a portion ofthe polycrystalline diamond element to a leaching solution such that theleaching solution contacts an exposed surface region of thepolycrystalline diamond table and at least a portion of the protectivecoating and 2) removing the polycrystalline diamond element from theleaching solution. The protective coating may be substantiallyimpermeable to the leaching solution.

In some examples, depositing the vaporized material over the selectedportion of the polycrystalline diamond element may comprise depositingthe vaporized material over the selected portion by at least one ofphysical vapor deposition, chemical vapor deposition, and hybridphysical-chemical vapor deposition. The physical vapor deposition maycomprise evaporative physical vapor deposition, electron beam physicalvapor deposition, sputter physical vapor deposition, cathodic arcphysical vapor deposition, and/or pulsed laser physical vapordeposition. In addition, the chemical vapor deposition may compriseatmospheric pressure chemical vapor deposition, low-pressure chemicalvapor deposition, high-vacuum chemical vapor deposition, aerosolassisted chemical vapor deposition, direct liquid injection chemicalvapor deposition, microwave plasma-assisted chemical vapor deposition,plasma-enhanced chemical vapor deposition, atomic layer chemical vapordeposition, metalorganic chemical vapor deposition, rapid thermalchemical vapor deposition, and/or hot wire chemical vapor deposition.

In various examples, depositing the vaporized material over the selectedportion of the polycrystalline diamond element may comprise depositingthe vaporized material over the selected portion by electrolessdeposition, spraying, and/or flame-spraying. Depositing the vaporizedmaterial over the selected portion of the polycrystalline diamondelement may also comprise rotating the polycrystalline diamond elementrelative to a vaporized material source.

In at least one example, the method may comprise drying the protectivecoating. The method may further comprise bonding the protective coatingto the selected portion of the polycrystalline diamond element. Themethod may also comprise removing at least a portion of the protectivecoating from the polycrystalline diamond element. The method mayadditionally comprise surrounding at least a portion of the protectivecoating with a substantially inert layer

In some examples, the protective coating may have a thickness of betweenapproximately 1 and 10 μm. In one example, the polycrystalline diamondelement may further comprise a substrate bonded to the polycrystallinediamond table. In this example, the selected portion may comprise atleast a portion of a surface of the polycrystalline diamond table and atleast a portion of a surface of the substrate.

In at least one embodiment, the method may comprise forming a ceramiccoating over a selected portion of the polycrystalline diamond element.The ceramic coating may comprise a nitride material and/or a carbidematerial (e.g., TiN, CrN, TiAlN, CrC, AlTiN, ZrN, TiCN, etc.).

Features from any of the described embodiments may be used incombination with one another in accordance with the general principlesdescribed herein. These and other embodiments, features, and advantageswill be more fully understood upon reading the following detaileddescription in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate a number of exemplary embodimentsand are a part of the specification. Together with the followingdescription, these drawings demonstrate and explain various principlesof the instant disclosure.

FIG. 1 is a perspective view of an exemplary superabrasive elementaccording to at least one embodiment.

FIG. 2 is a cross-sectional side view of an exemplary superabrasiveelement that is at least partially surrounded by a coating according toat least one embodiment.

FIG. 3 is cross-sectional side view of the exemplary superabrasiveelement illustrated in FIG. 2.

FIG. 4 is a perspective view of an exemplary drill bit according to atleast one embodiment.

FIG. 5 is a top view of the exemplary drill bit illustrated in FIG. 4.

FIG. 6 is a partial cut-away perspective view of an exemplary thrustbearing apparatus according to at least one embodiment.

FIG. 7 is a partial cut-away perspective view of an exemplary radialbearing apparatus according to at least one embodiment.

FIG. 8 is a partial cut-away perspective view of an exemplarysubterranean drilling system according to at least one embodiment.

FIG. 9 is a flow diagram of an exemplary method of processing asuperabrasive element according to at least one embodiment.

FIG. 10 is a flow diagram of an exemplary method of processing asuperabrasive element according to further embodiments.

Throughout the drawings, identical reference characters and descriptionsindicate similar, but not necessarily identical, elements. While theexemplary embodiments described herein are susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and will be described in detailherein. However, the exemplary embodiments described herein are notintended to be limited to the particular forms disclosed. Rather, theinstant disclosure covers all modifications, equivalents, andalternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The instant disclosure is directed to superabrasive articles, such assuperabrasive cutting elements and superabrasive bearing elements. Asused herein, the terms “superabrasive” and “superhard” may refer tomaterials exhibiting a hardness exceeding a hardness of tungstencarbide. For example, a superabrasive article may represent an articleof manufacture, at least a portion of which may exhibit a hardnessexceeding the hardness of tungsten carbide. The superabrasive articlesdisclosed herein may be used in a variety of applications, such asdrilling tools (e.g., compacts, cutting elements, gage trimmers, etc.),machining equipment, bearing apparatuses, wire-drawing machinery, andother apparatuses. The instant disclosure is also directed to methods ofprocessing superabrasive articles.

FIG. 1 is a perspective view of an exemplary superabrasive element 10according to at least one embodiment. As illustrated in FIG. 1,superabrasive element 10 may comprise a layer or superabrasive table 14affixed to or formed upon a substrate 12. Superabrasive table 14 may beaffixed to substrate 12 at interface 26. Superabrasive element 10 maycomprise a rear face 18 and a substrate side surface 16 formed bysubstrate 12. Superabrasive element 10 may also comprise a superabrasiveface 20, a superabrasive side surface 22, and a superabrasive edge 24formed by superabrasive table 14. Superabrasive edge 24 may comprise anangular or rounded edge formed at the intersection of superabrasive sidesurface 22 and superabrasive face 20. In some embodiments, superabrasiveedge 24 may comprise a chamfered surface extending between superabrasiveside surface 22 and superabrasive face 20.

Substrate 12 may comprise any suitable material on which superabrasivetable 14 may be formed. In at least one embodiment, substrate 12 maycomprise a cemented carbide material, such as a cobalt-cemented tungstencarbide material or any other suitable material. Further, substrate 12may include a suitable metal-solvent catalyst material, such as, forexample, cobalt, nickel, iron, and/or alloys thereof. Substrate 12 mayalso include any other suitable material including, without limitation,cemented carbides such as titanium carbide, niobium carbide, tantalumcarbide, vanadium carbide, chromium carbide, and/or combinations of anyof the preceding carbides cemented with iron, nickel, cobalt, and/oralloys thereof.

Superabrasive table 14 may be formed of any suitable superabrasiveand/or superhard material or combination of materials, including, forexample PCD. According to some embodiments, superabrasive table 14 maycomprise cubic boron nitride, silicon carbide, diamond, and/or mixturesor composites including one or more of the foregoing materials.

Superabrasive table 14 may be formed using any suitable technique. Forexample, superabrasive table 14 may comprise a PCD layer formed bysubjecting a plurality of diamond particles (e.g., diamond particleshaving an average particle size between approximately 0.5 μm andapproximately 150 μm) to a HPHT sintering process in the presence of ametal-solvent catalyst, such as cobalt, nickel, iron, and/or any othersuitable group VIII element. During a HPHT sintering process, adjacentdiamond crystals in a mass of diamond particles may become bonded to oneanother, forming a PCD table comprising bonded diamond crystals. In oneexample, diamond crystals in superabrasive table 14 may have an averagegrain size of approximately 20 μm or less. Further, during a HPHTsintering process, diamond grains may become bonded to an adjacentsubstrate 12 at interface 26.

According to various embodiments, superabrasive table 14 may be formedby placing diamond particles adjacent to a substrate 12 comprisingcemented tungsten carbide. The resulting sintered PCD layer may includevarious interstitial materials, including, for example, cobalt,tungsten, and/or tungsten carbide. For example, tungsten and/or tungstencarbide may be swept into the PCD layer from substrate 12 during HPHTsintering. In some examples, a liquefied metal-solvent catalyst fromsubstrate 12 (e.g., cobalt from a cobalt-cemented tungsten carbidesubstrate) may dissolve and carry tungsten and/or tungsten carbide fromsubstrate 12 into a diamond mass used to form superabrasive table 14during HPHT sintering. Tungsten and/or tungsten carbide particles mayalso be intentionally mixed with diamond particles prior to formingsuperabrasive table 14.

FIG. 2 is a cross-sectional side view of an exemplary superabrasiveelement 10 that is at least partially surrounded by a coating 28according to at least one embodiment. As shown in FIG. 2, coating 28 maybe disposed on at least a portion of superabrasive element 10. Forexample, coating 28 may be disposed on substrate 12 such that coating 28covers substantially all exposed surface portions of substrate 12. Insome examples, coating 28 may cover a portion of superabrasive table 14.Coating 28 may comprise any material suitable for protecting substrate12 by preventing or inhibiting corrosion of substrate 12 during leachingof superabrasive element 10, including, without limitation, a ceramicmaterial or other suitable coating material. In at least one example, asuitable ceramic material may include, for example, TiN, CrN, TiAlN,CrC, AlTiN, ZrN, and/or TiCN.

Coating 28 may be coated onto portions of superabrasive element 10 usingany suitable coating technique, without limitation. In at least oneembodiment, coating 28 may be coated onto portions of superabrasiveelement 10 using a suitable physical vapor deposition (“PVD”) process.In a PVD process, a material used to form coating 28 may be vaporizedand deposited onto surface portions of superabrasive element 10.Examples of suitable PVD processes include, for example, evaporativePVD, electron beam PVD, sputter PVD, cathodic arc PVD, and/or pulsedlaser PVD.

A PVD process may be conducted at relatively low temperatures of about500° C. or less. During a PVD process, superabrasive element 10 may berotated relative to a source generating the vaporized material to obtaina relatively even or complete coating on coated portions ofsuperabrasive element 10. Coating 28 may exhibit a desired thickness.

In some embodiments, coating 28 may be coated onto portions ofsuperabrasive element 10 using a suitable chemical vapor deposition(“CVD”) process. In a CVD process, one or more volatile reagents may bevaporized and heated and portions of superabrasive element 10 may beexposed to the vaporized reagents. The vaporized reagents may reactand/or decompose on surface portions of superabrasive element 10,forming a coating on the surface portions. Examples of suitable CVDprocesses include, without limitation, atmospheric pressure CVD,low-pressure CVD, high-vacuum CVD, aerosol assisted CVD, direct liquidinjection CVD, microwave plasma-assisted CVD, plasma-enhanced CVD,atomic layer CVD, metalorganic CVD, rapid thermal CVD, and/or hot wireCVD.

In some examples, a CVD process may be conducted at relatively hightemperatures of about 1300° C. or less. The CVD process may produce arelatively even coating on coated portions of superabrasive element 10.A hybrid physical-chemical vapor deposition process may also be used tocoat portions of superabrasive element 10. In at least one embodiment,at least a portion of superabrasive element 10 may be coated using anelectroless deposition technique, in which coating 28 is deposited on aconductive surface portion of superabrasive element 10. In variousembodiments, coating 28 may be sprayed and/or flame sprayed onto asurface of superabrasive element 10.

In some embodiments, after coating 28 is applied to at least a portionof superabrasive element 10, coating 28 may be dried to form a solid orrelatively solid coating. For example, coating 28 may be applied tosuperabrasive element 10 as a liquid composition, and coating 28 may bedried using any suitable drying technique, without limitation. Invarious examples, coating 28 may be applied to superabrasive element 10in such a manner that coating 28 comprises a relatively solid coatinglayer upon or immediately following deposition on superabrasive element10.

According to at least one embodiment, coating 28 may be bonded and/orotherwise adhered to at least a portion of substrate 12 and/orsuperabrasive table 14. For example, coating 28 may be bonded tosuperabrasive element 10 as coating 28 is applied to at least a portionof superabrasive element 10. In various embodiments, coating 28 may beadhered to superabrasive element 10 after coating 28 is applied to atleast a portion of superabrasive element 10. For example, coating 28 maybe heated, dried, and/or subjected to any other suitable conditionsresulting in coating 28 becoming adhered to superabrasive element 10.

Coating 28 may be formed to any suitable thickness. In variousembodiments, coating 28 may be formed to a thickness that prevents aleaching solution from coming into contact with portions ofsuperabrasive element 10, such as substrate 12, during leaching ofsuperabrasive table 14. Accordingly, coating 28 may protect substrate 12from pitting and other corrosion due to exposure to a leaching solution.Coating 28 may be formed to a thickness that facilitates suitableadhesion of coating 28 to portions of superabrasive element 10.Optionally, coating 28 may have a relatively even thickness on coatedportions of superabrasive element 10. In some examples, coating 28 mayhave a thickness of less than approximately 6 μm. In additionalexamples, coating 28 may have a thickness of between approximately 1 and10 μm. In at least one example, coating 28 may have a thickness ofbetween approximately 2 and 3 μm.

Coating 28 may comprise one or more layers of material. In someexamples, coating 28 may comprise multiple layers of coating material.The multiple layers of coating material may comprise one or more coatingmaterials. For example, various layers of material in coating 28 maycomprise different materials. In at least one embodiment, the multiplelayers in coating 28 may be formed at different times. For example, afirst coating layer may be formed directly on at least a portion ofsubstrate 12 and/or superabrasive table 14. Subsequently, a secondcoating layer may be formed on the first coating layer. The firstcoating layer and the second coating layer may be formed of relativelythe same materials. In some embodiments, the first coating layer and thesecond coating layer may be formed of different materials. In variousembodiments, additional coating layers formed of relatively the sameand/or different materials as the first coating layer and the secondcoating layer may also be formed.

FIG. 3 is cross-sectional side view of the exemplary superabrasiveelement 10 illustrated in FIG. 2 according to some embodiments. Asillustrated in FIG. 3, superabrasive element 10 may be at leastpartially surrounded by a protective layer 30. Protective layer 30 maycomprise a substantially inert material. In some examples, protectivelayer 30 may comprise a substantially inert cup, such as, for example, apolytetrafluoroethylene (“PTFE”) cup.

The inert cup may be sized to fit tightly around and cover at least aportion of substrate 12. In some embodiments, as illustrated in FIG. 3,the inert cup may be configured to fit around substrate 12 that iscoated with coating 28. In some examples, protective layer 30 may alsocover at least a portion of superabrasive table 14. Protective layer 30may prevent or reduce an amount of leaching solution coming into contactwith coating 28 and/or substrate 12 during leaching of superabrasivetable 14.

A superabrasive element 10 that is at least partially coated withcoating 28 and/or protective layer 30 may be exposed to a leachingsolution used in leaching various materials from superabrasive table 14.In at least one example, a corrosive leaching solution may be used toremove a metal-solvent catalyst from interstitial spaces between diamondgrains in superabrasive table 14. According to various embodiments, theleaching solution may comprise various solvents, acids, and/or othersuitable reagents, including, without limitation, water, peroxide,nitric acid, hydrofluoric acid, and/or hydrochloric acid. Superabrasiveelement 10 may be exposed to the leaching solution for any suitableperiod of time. For example, superabrasive element 10 may be exposed tothe leaching solution until various interstitial materials, such as, forexample, a metal-solvent catalyst, are removed from superabrasive table14 to a desired depth.

Although small amounts of leaching solution may seep between protectivelayer 30 and coating 28 during leaching of superabrasive element 10, therate of corrosion of coating 28 due to the leaching solution may bereduced in comparison with a superabrasive element 10 that does notinclude protective layer 30. Protective layer 30 may therefore inhibitthe leaching solution from chemically corroding coating 28 and/orsubstrate 12. Accordingly, a superabrasive element 10 that includes aprotective layer 30 and a coating 28 may be exposed to a leachingsolution for relatively longer periods of time and/or may be exposed torelatively stronger leaching solutions than conventional superabrasiveelements.

Following leaching of superabrasive table 14, protective layer 30 may beremoved from superabrasive element 10. Further, coating 28 may beremoved from superabrasive element 10 following leaching. Coating 28 maybe removed using any suitable material removal technique including,without limitation, CG-grinding, chemical sand blasting, and/or beadblasting. According to various embodiments, a chamfered cutting edge 24(e.g., chamfered cutting edge 24 in FIG. 1) may be formed prior to orfollowing leaching. In at least one example, chamfered cutting edge 24may be formed using the same material removal technique used to removecoating 28.

FIGS. 4 and 5 are a perspective view and a top view, respectively, of anexemplary drill bit 42 according to at least one embodiment. Drill bit42 may represent any type or form of earth-boring or drilling tool,including, for example, a rotary drill bit.

As illustrated in FIGS. 4 and 5, drill bit 42 may comprise a bit body 44having a longitudinal axis 52. Bit body 44 may define a leading endstructure for drilling into a subterranean formation by rotating bitbody 44 about longitudinal axis 52 and applying weight to bit body 44.Bit body 44 may include radially and longitudinally extending blades 46with leading faces 48 and a threaded pin connection 50 for connectingbit body 44 to a drill string.

At least one cutting element 58 may be coupled to bit body 44. Forexample, as shown in FIGS. 4 and 5, a plurality of cutting elements 58may be coupled to blades 46. Cutting elements 58 may comprise anysuitable superabrasive cutting elements, without limitation. In at leastone embodiment, cutting elements 58 may be configured according topreviously described superabrasive element 10. For example, each cuttingelement 58 may include a superabrasive table 60, such as a PCD table,bonded to a substrate 62.

Circumferentially adjacent blades 46 may define so-called junk slots 54therebetween. Junk slots 54 may be configured to channel debris, such asrock or formation cuttings, away from cutting elements 58 duringdrilling. Rotary drill bit 42 may also include a plurality of nozzlecavities 56 for communicating drilling fluid from the interior of rotarydrill bit 42 to cutting elements 58.

FIGS. 6 and 7 depict an example of a rotary drill bit 42 that employs atleast one cutting element 58 comprising a superabrasive table 60fabricated and structured in accordance with the disclosed embodiments,without limitation. Rotary drill bit 42 may optionally represent anynumber of earth-boring tools or drilling tools, including, for example,core bits, roller-cone bits, fixed-cutter bits, eccentric bits, bicenterbits, reamers, reamer wings, or any other downhole tool includingsuperabrasive cutting elements and discs, without limitation.

The superabrasive elements and discs disclosed herein may also beutilized in applications other than cutting technology. For example,embodiments of superabrasive elements disclosed herein may also form allor part of heat sinks, wire dies, bearing elements, cutting elements,cutting inserts (e.g., on a roller cone type drill bit), machininginserts, or any other article of manufacture as known in the art. Thus,superabrasive elements and discs, as disclosed herein, may be employedin any suitable article of manufacture that includes a superabrasiveelement, disc, or layer. Other examples of articles of manufacture thatmay incorporate superabrasive elements as disclosed herein may be foundin U.S. Pat. Nos. 4,811,801; 4,268,276; 4,468,138; 4,738,322; 4,913,247;5,016,718; 5,092,687; 5,120,327; 5,135,061; 5,154,245; 5,460,233;5,544,713; and 6,793,681, the disclosure of each of which isincorporated herein, in its entirety, by this reference.

In some embodiments, a rotor and a stator, such as a rotor and a statorused in a thrust bearing apparatus, may each include at least onesuperabrasive element according to the embodiments disclosed herein. Forexample, U.S. Pat. Nos. 4,410,054; 4,560,014; 5,364,192; 5,368,398; and5,480,233, the disclosure of each of which is incorporated herein, inits entirety, by this reference, disclose subterranean drilling systemsthat include bearing apparatuses utilizing superabrasive elements asdisclosed herein.

FIG. 6 is partial cut-away perspective view of an exemplarythrust-bearing apparatus 64 according to at least one embodiment.Thrust-bearing apparatus 64 may utilize any of the disclosedsuperabrasive element embodiments as bearing elements 70. Thrust-bearingapparatus 64 may also include bearing assemblies 66. Each bearingassembly 66 may include a support ring 68 fabricated from a material,such as steel, stainless steel, or any other suitable material, withoutlimitation.

Each support ring 68 may include a plurality of recesses 69 configuredto receive corresponding bearing elements 70. Each bearing element 70may be mounted to a corresponding support ring 68 within a correspondingrecess 69 by brazing, welding, press-fitting, using fasteners, or anyanother suitable mounting technique, without limitation. One or more ofbearing elements 70 may be configured in accordance with any of thedisclosed superabrasive element embodiments. For example, each bearingelement 70 may include a substrate 72 and a superabrasive table 74comprising a PCD material. Each superabrasive table 74 may form abearing surface 76.

Bearing surfaces 76 of one bearing assembly 66 may bear against opposingbearing surfaces 76 of a corresponding bearing assembly 66 inthrust-bearing apparatus 64, as illustrated in FIG. 6. For example, afirst bearing assembly 66 of thrust-bearing apparatus 64 may be termed a“rotor.” The rotor may be operably coupled to a rotational shaft. Asecond bearing assembly 66 of thrust-bearing apparatus 64 may be heldsubstantially stationary relative to the first bearing assembly 66 andmay be termed a “stator.”

FIG. 7 is a partial cut-away perspective view of a radial bearingapparatus 78 according to another embodiment. Radial bearing apparatus78 may utilize any of the disclosed superabrasive element embodiments asbearing elements 84 and 86. Radial bearing apparatus 78 may include aninner race 80 positioned generally within an outer race 82. Inner race80 may include a plurality of bearing elements 84 affixed thereto, andouter race 80 may include a plurality of corresponding bearing elements86 affixed thereto. One or more of bearing elements 84 and 86 may beconfigured in accordance with any of the superabrasive elementembodiments disclosed herein.

Inner race 80 may be positioned generally within outer race 82. Thus,inner race 80 and outer race 82 may be configured such that bearingsurfaces 85 defined by bearing elements 84 and bearing surfaces 87defined by bearing elements 86 may at least partially contact oneanother and move relative to one another as inner race 80 and outer race82 rotate relative to each other. According to various embodiments,thrust-bearing apparatus 64 and/or radial bearing apparatus 78 may beincorporated into a subterranean drilling system.

FIG. 8 is a partial cut-away perspective view of an exemplarysubterranean drilling system 88 that includes a thrust-bearing apparatus64 according to at least one embodiment. The subterranean drillingsystem 88 may include a housing 90 enclosing a downhole drilling motor92 (i.e., a motor, turbine, or any other suitable device capable ofrotating an output shaft, without limitation) that is operably connectedto an output shaft 94.

The thrust-bearing apparatus 64 shown in FIG. 8 may be operably coupledto downhole drilling motor 92. A rotary drill bit 96, such as a rotarydrill bit configured to engage a subterranean formation and drill aborehole, may be connected to output shaft 94. As illustrated in FIG. 8,rotary drill bit 96 may be a roller cone bit comprising a plurality ofroller cones 98. According to some embodiments, rotary drill bit 96 maycomprise any suitable type of rotary drill bit, such as, for example, aso-called fixed-cutter drill bit. As a borehole is drilled using rotarybit 96, pipe sections may be connected to subterranean drilling system88 to form a drill string capable of progressively drilling the boreholeto a greater depth within a subterranean formation.

A first thrust-bearing assembly 66 in thrust-bearing apparatus 64 may beconfigured as a rotor that is attached to output shaft 94 and a secondthrust-bearing assembly 66 in thrust-bearing apparatus 64 may beconfigured as a stator. During a drilling operation using subterraneandrilling system 88, the rotor may rotate in conjunction with outputshaft 94 and the stator may remain substantially stationary relative tothe rotor.

According to various embodiments, drilling fluid may be circulatedthrough downhole drilling motor 92 to generate torque and effectrotation of output shaft 94 and rotary drill bit 96 attached thereto sothat a borehole may be drilled. A portion of the drilling fluid may alsobe used to lubricate opposing bearing surfaces of bearing elements 70 onthrust-bearing assemblies 66.

FIG. 9 illustrates an exemplary method 100 of processing apolycrystalline diamond element according to at least one embodiment. Asshown in FIG. 9, at step 102 a vaporized material may be deposited overa selected portion of a polycrystalline diamond element (e.g.,superabrasive element 10 illustrated in FIG. 2) to form a protectivecoating (e.g., coating 28 illustrated in FIG. 2) over the selectedportion. The polycrystalline diamond element may comprise apolycrystalline diamond table (e.g., superabrasive table 14 illustratedin FIG. 2). In some examples, the polycrystalline diamond table may bebonded to a suitable substrate (e.g., substrate 12 illustrated in FIG.2), such as, for example, a tungsten carbide substrate. In variousembodiments, the protective coating may also be formed on at least aportion of the polycrystalline diamond table and/or at least a portionof the substrate. The polycrystalline diamond element may be rotatedrelative to a vaporized material source during deposition.

The vaporized material may be deposited over the selected portion of thepolycrystalline diamond table using any suitable coating technique,including, for example, physical vapor deposition and/or chemical vapordeposition. The physical vapor deposition may comprise evaporativephysical vapor deposition, electron beam physical vapor deposition,sputter physical vapor deposition, cathodic arc physical vapordeposition, and/or pulsed laser physical vapor deposition.

The chemical vapor deposition may comprise atmospheric pressure chemicalvapor deposition, low-pressure chemical vapor deposition, high-vacuumchemical vapor deposition, aerosol assisted chemical vapor deposition,direct liquid injection chemical vapor deposition, microwaveplasma-assisted chemical vapor deposition, plasma-enhanced chemicalvapor deposition, atomic layer chemical vapor deposition, metalorganicchemical vapor deposition, rapid thermal chemical vapor deposition,and/or hot wire chemical vapor deposition. In some examples, thevaporized material may be deposited over the selected portion of thepolycrystalline diamond element by electroless deposition, spraying,and/or flame-spraying.

The protective coating may include any suitable material or combinationof materials, including, for example, a ceramic material such as anitride and/or a carbide material (e.g., TiN, CrN, TiAlN, CrC, AlTiN,ZrN, TiCN, etc.). According to at least one embodiment, the protectivecoating may be bonded and/or otherwise adhered to at least a portion ofthe substrate and/or the polycrystalline diamond table. The protectivecoating may also be dried after it is formed over the selected portionof the polycrystalline diamond element.

At least a portion of the substrate may also be surrounded with asubstantially inert layer (e.g., protective layer 30 illustrated in FIG.3). For example, an inert PTFE cup may be placed around thepolycrystalline diamond element so that the cup surrounds at least aportion of the substrate. The substantially inert layer may alsosurround at least a portion of the coating disposed on thepolycrystalline diamond element. In at least one embodiment, the inertlayer may comprise a preformed layer of material, such as a cup, that isconfigured to closely surround at least a portion of the substrate,polycrystalline diamond table, and/or coating disposed on thepolycrystalline diamond element. In at least one example, the inertlayer may be formed such that it surrounds and/or frictionally engagesan outer portion of the polycrystalline diamond element and/or coating.In some embodiments, the inert layer may be adhered to an outer portionof the polycrystalline diamond element and/or coating using, forexample, an adhesive.

At step 104, at least a portion of the polycrystalline diamond elementmay be exposed to a leaching solution such that the leaching solutioncontacts an exposed surface region of the polycrystalline diamond tableand at least a portion of the protective coating. According to variousembodiments, the leaching solution may comprise various solvents, acids,and/or other suitable reagents, including, without limitation, water,peroxide, nitric acid, hydrofluoric acid, and/or hydrochloric acid. Thepolycrystalline diamond element may be exposed to the leaching solutionin any suitable manner. For example, the polycrystalline diamond elementmay be at least partially submerged in the leaching solution. Thepolycrystalline diamond element may be exposed to the leaching solutionuntil the polycrystalline diamond table is leached to a sufficientdepth. The coating may inhibit corrosion of the substrate duringleaching, thereby preventing pitting of the substrate.

At step 106, the polycrystalline diamond element may be removed from theleaching solution. For example, the polycrystalline diamond element maybe removed from the leaching solution once the polycrystalline diamondtable has been leached to a desired depth. Once the polycrystallinediamond element has been removed from the leaching solution, theprotective coating may also be removed from the substrate. The coatingmay be removed using any suitable technique including, withoutlimitation, CG-grinding, chemically sand blasting, and/or bead blasting.According to various embodiments, a chamfered cutting edge may be formedon the polycrystalline diamond table following leaching. For example,the chamfered cutting edge may be formed using the same technique usedto remove the coating.

FIG. 10 illustrates an exemplary method 200 of processing apolycrystalline diamond element according to some embodiments. As shownin FIG. 10, at step 202 a ceramic coating may be formed over a selectedportion of a polycrystalline diamond element comprising apolycrystalline diamond table. At step 204, at least a portion of thepolycrystalline diamond element may be exposed to a leaching solutionsuch that the leaching solution contacts an exposed surface region ofthe polycrystalline diamond table and at least a portion of the ceramiccoating. At step 206, the polycrystalline diamond element may be removedfrom the leaching solution.

The preceding description has been provided to enable others skilled inthe art to best utilize various aspects of the exemplary embodimentsdescribed herein. This exemplary description is not intended to beexhaustive or to be limited to any precise form disclosed. Manymodifications and variations are possible without departing from thespirit and scope of the instant disclosure. It is desired that theembodiments described herein be considered in all respects illustrativeand not restrictive and that reference be made to the appended claimsand their equivalents for determining the scope of the instantdisclosure.

Unless otherwise noted, the terms “a” or “an,” as used in thespecification and claims, are to be construed as meaning “at least oneof.” In addition, for ease of use, the words “including” and “having,”as used in the specification and claims, are interchangeable with andhave the same meaning as the word “comprising.”

What is claimed is:
 1. A method of processing a polycrystalline diamondelement, comprising: forming a protective coating over a selectedportion of a polycrystalline diamond element comprising apolycrystalline diamond table having a polycrystalline diamond face, thepolycrystalline diamond element comprising a rear surface and a sidesurface extending between the polycrystalline diamond face and the rearsurface; bonding the protective coating to the selected portion of thepolycrystalline diamond element; surrounding at least a portion of theprotective coating with a protective layer; exposing a portion of thepolycrystalline diamond element extending from an open end of theprotective layer to a leaching solution such that the leaching solutioncontacts an exposed surface region of the polycrystalline diamond tableand at least a portion of the protective layer; removing thepolycrystalline diamond element from the leaching solution; wherein: theprotective coating is substantially impermeable to the leachingsolution; the protective coating covers at least a portion of the sidesurface of the polycrystalline diamond element and the rear surface ofthe polycrystalline diamond element.
 2. The method of claim 1, whereinforming the protective coating over the selected portion of thepolycrystalline diamond element comprises depositing a vaporizedmaterial over the selected portion by at least one of physical vapordeposition, chemical vapor deposition, and hybrid physical-chemicalvapor deposition.
 3. The method of claim 2, wherein the physical vapordeposition comprises at least one of evaporative physical vapordeposition, electron beam physical vapor deposition, sputter physicalvapor deposition, cathodic arc physical vapor deposition, and pulsedlaser physical vapor deposition.
 4. The method of claim 2, wherein thechemical vapor deposition comprises at least one of atmospheric pressurechemical vapor deposition, low-pressure chemical vapor deposition,high-vacuum chemical vapor deposition, aerosol assisted chemical vapordeposition, direct liquid injection chemical vapor deposition, microwaveplasma-assisted chemical vapor deposition, plasma-enhanced chemicalvapor deposition, atomic layer chemical vapor deposition, metalorganicchemical vapor deposition, rapid thermal chemical vapor deposition, andhot wire chemical vapor deposition.
 5. The method of claim 1, whereinforming the protective coating over the selected portion of thepolycrystalline diamond element comprises depositing the vaporizedmaterial over the selected portion by at least one of electrolessdeposition, spraying, and flame-spraying.
 6. The method of claim 1,wherein forming the protective coating over the selected portion of thepolycrystalline diamond element comprises rotating the polycrystallinediamond element relative to a vaporized material source.
 7. The methodof claim 1, further comprising removing the protective layer and atleast a portion of the protective coating from the polycrystallinediamond element.
 8. The method of claim 1, wherein the protectivecoating has a thickness of between approximately 1 and 10 μm.
 9. Themethod of claim 1, wherein the protective layer comprises asubstantially inert layer.
 10. The method of claim 1, wherein theprotective layer abuts at least a portion of the protective coating. 11.The method of claim 1, wherein surrounding at least the portion of theprotective coating with the protective layer comprises placing, afterforming the protective coating over the selected portion of thepolycrystalline diamond element, the protective layer around at least aportion of the polycrystalline diamond element and at least the portionof the protective coating.
 12. The method of claim 1, wherein: thepolycrystalline diamond element further comprises a substrate bonded tothe polycrystalline diamond table; the selected portion comprises atleast a portion of a surface of the polycrystalline diamond table and atleast a portion of a surface of the substrate.
 13. A method ofprocessing a polycrystalline diamond element, comprising: forming aceramic coating over a selected portion of a polycrystalline diamondelement comprising a polycrystalline diamond table having apolycrystalline diamond face, the polycrystalline diamond elementcomprising a rear surface and a side surface extending between thepolycrystalline diamond face and the rear surface; surrounding at leasta portion of the ceramic coating with a protective layer; exposing atleast a portion of the polycrystalline diamond element to a leachingsolution such that the leaching solution contacts an exposed surfaceregion of the polycrystalline diamond table and at least a portion ofthe protective layer; removing the polycrystalline diamond element fromthe leaching solution; wherein the ceramic coating covers at least aportion of the side surface of the polycrystalline diamond element andsubstantially covers the rear surface of the polycrystalline diamondelement.
 14. The method of claim 13, wherein the ceramic coatingcomprises at least one of a nitride material and a carbide material. 15.The method of claim 13, wherein the ceramic coating comprises at leastone of TiN, CrN, TiAlN, CrC, AlTiN, ZrN, and TiCN.
 16. The method ofclaim 13, wherein forming a ceramic coating over the selected portion ofthe polycrystalline diamond element comprises depositing a vaporizedmaterial over the selected portion of the polycrystalline diamondelement.
 17. The method of claim 13, further comprising removing theprotective layer and at least a portion of the ceramic coating from thepolycrystalline diamond element.
 18. The method of claim 13, wherein theprotective layer comprises a substantially inert layer.
 19. The methodof claim 13, wherein the protective layer abuts at least a portion ofthe ceramic coating.
 20. The method of claim 13, wherein the surroundingat least the portion of the ceramic coating with the protective layercomprises placing a polymer cup around at least a portion of thepolycrystalline diamond element and at least the portion of the ceramiccoating.
 21. The method of claim 1, wherein the portion of theprotective coating covering the rear surface of the polycrystallinediamond element is disposed between the rear surface of thepolycrystalline diamond element and a portion of the protective layer.22. The method of claim 1, wherein surrounding at least the portion ofthe protective coating with the protective layer comprises enclosing atleast the portion of the protective coating within a polymer cup. 23.The method of claim 1, wherein the protective coating comprises a solidmaterial.